A transmitter of a wireless communication system improves non-linear characteristics of a power amplifier by use of a predistortion apparatus of a Digital Pre-Distortion (DPD) power amplifier.
The predistortion apparatus pre-distorts a digital signal input to the DPD power amplifier such that an input signal and an output signal of the DPD power amplifier have linear characteristics. The predistortion apparatus pre-distorts the input signal using an inverse function of the non-linear characteristic of the DPD power amplifier generated using an Amplitude Modulation-to-Amplitude Modulation (AM-AM) Look Up Table (LUT), and an AM-to-Phase Modulation (AM-PM) LUT.
The transmitter determines a resolution bit width lest a quantization noise level affect its performance. The LUT of the predistortion apparatus has a memory capacity determined according to the number of data of the LUT corresponding to the resolution bit width. That is, when the resolution bit width rises and the number of data increases, the memory capacity for the LUT of the predistortion apparatus also increases.
As discussed above, when the memory capacity of the LUT increases, disadvantageously, the transmitter raises the product cost, and the time taken to update the LUT extends. In addition, the increases of the LUT update time and the memory capacity consume more of the transmitter power.